Organ	Visibility	Location	Retroperitoneal Versus Intraperitoneal	Fixed Versus Mobile	Appearance Specifics	Plain Film Abnormalities
Esophagus	Air occasionally visible in the cervical region	Anterior and left of spine from laryngopharynx to diaphragm	Not applicable	Fixed	None on plain film	Abnormalities, including dilatation or neoplasm, may present as posterior mediastinal mass (hiatal hernia)
Stomach	Air in the fundus on upright with inferior fluid level; spreads to body of stomach and may outline rugae on supine image	Magenblase immediately inferior to left lung base on upright image; should not extend to midline or lateral body	Intraperitoneal	Fixed proximal and distal; mobile body	None on plain film	Displacement of magenblase laterally suggests hepatomegaly
Duodenum	Occasional air in bulb	Right upper quadrant medially	Retroperitoneal (most)	Fixed	None	None
Small bowel	Occasional air-filled small segment	Most of abdomen; jejunum primarily left upper quadrant and middle lower ileum	Intraperitoneal	Mobile	Small, thin mucosal folds	Long air-filled segments; dilated air filled (>3 cm)
Cecum	Fluid feces and gas bubbles mixed	Right lower quadrant (RLQ)	Intraperitoneal	Mobile, usually RLQ location	None	Distension (>10 cm risk of rupture); volvulus (“coffee bean” sign)
Appendix	May be visible gas in appendix	Considerable variation, although usually in RLQ	Intraperitoneal	Can move with the cecum	None	Normal or may show slight distension of adjacent ileum; possible appendicolith
Ascending and descending colon	Visible gas in haustra	Ascending along right flank; descending along left flank	Retroperitoneal	Fixed	Widely spaced, thick mucosal folds; lateral margin of both should be within 2 to 3 mm of adjacent flank stripe (fat plane medial to abdominal muscle wall); splenic flexure should be most superior portion of colon	Dilatation

Cholelithiasis (Gallstones)

Background

The incidence of gallstones in patients in the United States approaches 20% of men and 35% of women by the age of 75 years;²⁵ thus, gallstones exhibit a greater prevalence in women and in older age groups. Obesity and certain diseases also are associated with the development of gallstones (Table 30-2 ).

TABLE 30-2

ASSOCIATED FACTORS FOR GALLSTONE FORMATION

Associated Factors	Comments
Obesity	Rapid weight loss resulting in increased risk of symptomatic gallstone formation¹⁸
Increasing age	Associated with increased cholesterol secretion
Northern European ethnic group	Associated with increased cholesterol secretion
Estrogen replacement therapy and oral contraceptive use	Increases biliary output of cholesterol and also reduces synthesis of bile acid in women
Pregnancy	Associated with increased risk of gallstones and symptomatic gallbladder disease
Sickle-cell anemia or other hemolytic conditions	Hemolysis increases bilirubin excretion
Crohn disease	Disease of the terminal ileum causing disruption of bile acid reabsorption

From Johnston DE, Kaplan MM: Pathogenesis and treatment of gallstones, N Engl J Med 328:412, 1993; Liddle RA, Goldstein RB, Saxton J: Gallstone formation during weight-reduction dieting, Arch Intern Med 149:1750, 1989; Tait N, Little JM: The treatment of gallstones, BMJ 311:99, 1995.

Imaging Findings

Ultrasonography generally is the preferred imaging modality for evaluating patients for possible gallstones or biliary duct obstruction. Current high-resolution, real-time ultrasonography can identify gallstones as small as 2 mm. This technique is rapid and noninvasive and does not involve ionizing radiation. Gallstones produce hyperechoic foci with acoustic shadowing, and mobility of the stone usually is apparent (Fig. 30-1 ).5,16 The patient should fast for 4 or more hours because these stones can be missed in a contracted gallbladder.²⁶

FIG 30-1 Choleliths. Ultrasound image shows multiple echogenic foci within the gallbladder lumen *(arrows)* with posterior acoustic shadowing *(curved arrows).* Courtesy John A.M. Taylor, Seneca Falls, NY.

These stones may be imaged incidentally on plain film radiographs even in asymptomatic patients, but only 10% to 15% of them contain enough calcium to be visible (Figs. 30-2 through 30-4 ).^12,32 Oral cholecystography (OCG) requires the patient to take an oral contrast agent, which is absorbed from the bowel, excreted by the liver, and concentrated in the gallbladder (except when the gallbladder cystic duct is blocked or sometimes when the gallbladder is inflamed). The gallbladder also is not seen in cases of a lack of absorption or significant liver damage.

FIG 30-2 Choleliths. Two laminated and faceted calculi in the gallbladder characteristic of concretion calcifications *(arrows)*.

FIG 30-3 Oral cholecystographic appearance of gallstones. A, Oral cholecystogram with the patient in the recumbent position demonstrates several nonopaque stones within the gallbladder *(arrows)*. B, With the patient in the upright position, the stones float just above the fundus *(arrows)*. Courtesy John A.M. Taylor, Seneca Falls, NY.

FIG 30-4 Gallstones appearing as radiodense calculi of the right upper abdominal quadrant on an anteroposterior **(A)** and lateral lumbar projection **(B)** and in three other patients (C to E, *arrows)*. The horizontal radiolucent shadow *(arrowheads)* **(D)** represents air loculated in a skin fold.

Oral cholecystography does demonstrate most gallstones, but since the development of ultrasonography to accomplish this task, it is most useful for providing information about the functional status of the gallbladder (see Fig. 30-3 ).⁷ However, the clinical utility of this is still controversial. Table 30-3 lists the imaging techniques and the limitations of each of these key modalities used in visualizing gallstones.

TABLE 30-3

LIMITATIONS OF IMAGING TECHNIQUES FOR VISUALIZING GALLBLADDER STONES

Imaging Technique	Imaging Findings	Limitations
Plain film radiography	Single concretion or multiple calcific concretions; calcification may be central, homogeneous, or rim-like; when multiple, stones are often clustered together and faceted	The majority of nonopaque stones will not be visible.
Oral cholecystography	Single or multiple lucent-filling defects within opacified gallbladder; mobility of stones may be demonstrated by change in patient position	A number of conditions such as malabsorption, gastric outlet obstruction, inflammatory bowel disease, ileal disease, and liver disease may prevent opacification of the gallbladder.
Ultrasonography	Stones appear as intraluminal, echogenic, mobile foci that are gravity dependent and create an acoustic shadow	Small stones less than 2 mm in the presence of biliary sludge may prevent visualization; inadequate visualization may occur in obese patients.
Computed tomography (CT)	Single or multiple filling defects within gallbladder; stones may be densely calcified, rim calcified, or laminated; lucent filling defects within the bile may be seen with contrast-enhanced CT	Approximately 20% of gallstones are not identified on CT; CT is not considered a screening tool for uncomplicated cholelithiasis.
Magnetic resonance imaging (MRI)	Most gallstones have no signal on MRI and present as a signal void-filling defect within gallbladder.	Stones may be indistinguishable from polyps or tumors; MRI is not considered a screening tool for uncomplicated cholelithiasis.

Uncommonly, a noncontrasted gallbladder forms a radiodense “milk of calcium” bile, known as limy bile syndrome, that mimics the gallbladder’s appearance during OCG (Fig. 30-5 ). This is thought to develop from chronic obstruction of the cystic duct by one or more gallstones in patients with chronic cholecystitis. The duct obstruction leads to decreased gland function, bile stasis, and radiographically visible accumulations of radiodense calcium carbonate in viscous intraluminal bile. Reviewing the patient’s history to exclude any recent intake of contrast material (oral or intravenous) must be accomplished before a diagnosis of limy bile syndrome can be made. On radiographs, the fluid is found in the gravity-dependent portion of the gallbladder. The ultrasound appearance is not consistent because the composition of the milk of calcium bile varies from a semisolid to fluid suspension.

FIG 30-5 A, Milk of calcium bile. Multiple gallstones are noted in the lower portion of the gallbladder. The stones are contrasted by an opaque fluid of calcium carbonate, known as milk of calcium bile. B and C, A second case of minimal accumulation and a gallstone *(arrowheads)* with incidental observation of umbilical jewelry. Courtesy Ian D. McLean, LeClaire, IA.

“Porcelain gallbladder” describes extensive calcification of the wall of the gallbladder, also known as calcifying cholecystitis or cholecystopathic chronica calcarea (Figs. 30-6 and 30-7 ). Specifically, the term refers to the blue-greenish discoloration and brittle condition of the gallbladder observed during surgery. Patients generally are asymptomatic and are more commonly women (5 : 1 ratio). Concurrent gallstones are usual. A porcelain gallbladder is associated with higher incidence of adenocarcinoma of the gallbladder, typically warranting prophylactic excision. As with gallbladder stones and limy bile syndrome, a porcelain gallbladder is typically an incidental finding on plain film studies (Table 30-4).

TABLE 30-4

PLAIN FILM MANIFESTATIONS OF GALLBLADDER DISEASE

Condition	Radiographic Findings	Comments
Stones	Single calcific concretion or multiple calcific concretions; calcification may be central, homogeneous, or rim-like; when multiple stones, they often are clustered together and usually faceted; on erect films, stones may be layered in the dependent portion of the gallbladder	10% to 15% of stones are visible on plain radiographs
Limy bile syndrome (milk of calcium bile)	Radiopaque appearance of the gallbladder or bile ducts than may simulate contrast	Limy bile is caused by calcium carbonate precipitation in the bile; the main symptom are epigastralgia and right hypochondralgia
Porcelain gallbladder	Characteristic appearance is eggshell calcification in the right upper quadrant	Patients are generally asymptomatic

FIG 30-6 Porcelain gallbladder. Anteroposterior **(A)** and lateral **(B)** plain films exhibit curvilinear radiodense shadows in the right upper abdominal quadrant that correspond to partial calcification of the wall of the gallbladder. C, On computed tomography without contrast, the circumference of the gallbladder is calcified. Gallstones are not present *(arrows)*. Courtesy Kevin Paustian, Durant, IA.

FIG 30-7 A to C, Porcelain gallbladder in several patients *(arrows)*. The finding of a porcelain gallbladder typically warrants surgical excision because of the approximately 20% associated increased risk of developing gallbladder carcinoma.

Clinical Comments

Cholelithiasis usually is discovered incidentally during other studies. In the first 5 years after diagnosis, only approximately 10% of patients experience symptoms resulting from gallstones.³² Right upper quadrant pain is the most commonly reported symptom.³² The pain usually is steady, lasting for several hours. Radiation to the lower abdomen, back, or tip of the right scapula is common; vomiting may occur.⁵

Complications seen with gallstone disease include cholecystitis, choledocholithiasis, pancreatitis (migration of a stone to the distal common duct where the pancreatic duct enters), cholangitis, stone perforation of the duodenum or colon, and gallstone ileus (Table 30-5 ).^2,3,5,20,32 Symptomatic gallbladder disease may require surgical intervention if nonsurgical techniques such as lithotripsy (using strong ultrasound waves to break up the stone) are ineffective, unsuitable, or unavailable.³²

TABLE 30-5

COMPLICATIONS ASSOCIATED WITH GALLSTONES

Complications	Comments
Acute cholecystitis	May remit temporarily but sometimes progresses to gangrene and perforation
Choledocholithiasis	Gallstones obstructing the common bile duct
Cholangitis	Infection of the bile ducts after obstruction possible
Acute pancreatitis	Probably secondary to transient obstruction of the main pancreatic duct
Gallstone ileus	Follows perforation of the duodenum or bowel by gallstone; classic plain film triad: small bowel obstruction, biliary tract air, and an opaque concretion in the small bowel

From Johnston DE, Kaplan MM: Pathogenesis and treatment of gallstones, N Engl J Med 328:412, 1993.

Key Concepts

• The prevalence of cholelithiasis increases with age.

• It is more common in women.

• Obesity is a risk factor.

• Symptoms vary, and clinical correlation is required.

• Plain film radiography plays a minor role.

Colon Polyps

Background

Colon polyps are found in up to 12% of the population.³⁴ The adenomatous polyp is considered the precursor to colorectal cancer.¹⁷ Therefore, detection of colonic polyps is extremely important. Polyp size is a critical biomarker guiding clinical management. The incidence of malignancy increases with increased size of the polyp (Table 30-6 ). Most polyp development is incidental, but polyps may also appear as part of familial polyposis syndrome. Table 30-7 reviews the characteristics of several polyposis conditions.

TABLE 30-6

INCIDENCE OF MALIGNANCY IN RELATION TO POLYP SIZE

5 mm or less	5 mm to 10 mm	10 mm to 20 mm	More than 20 mm
<0.5%	1%–2.5%	10%	46%

From Thoeni RFL, Bischof TP: Colonic polyps. In Traveras JM, Ferrucci JT, editors: Radiology diagnosis-imaging-intervention, vol 4, Philadelphia, 1996, Lippincott-Raven.

TABLE 30-7

REVIEW OF POLYPOSIS CONDITIONS

Complications	Comments
Nonfamilial adenomatous polyps	Present in 30% of adults older than 50 years of age; malignancy correlates with polyp size, villous features, and degree of dysplasia
Familial adenomatous polyposis	Autosomal dominant; it begins to appear between ages of 10 and 35 years; colon cancer usually occurs by age 50 years
Gardner syndrome	Variant of familial adenomatous polyposis; it is characterized by extraintestinal osteomas, fibromas, and desmoid tumors
Familial juvenile polyposis	Autosomal dominant; most common—colon
Peutz-Jeghers syndrome	Autosomal dominant; mucocutaneous pigmented macules appear on the lips, buccal mucosa, and skin; 50% of patients develop malignancies in gastrointestinal and nonintestinal organs
Turcot syndrome	Autosomal recessive; central nervous system neoplasm

Imaging Findings

Conventional (optical) colonoscopy and barium examination are the most important methods for detecting polyps.³³ CT colonography is a newer, minimally invasive method for examination the colon for colorectal polyps; however, it is not widely accepted beyond the current indications of incomplete optical colonoscopy or patients unsafe for optical colonoscopy.

Polyps appear as discrete masses, sessile or pedunculated, which protrude into the lumen of the gut (Figs. 30-8 to 30-10

Only gold members can continue reading. Log In or Register to continue